The present invention relates to compositions containing polycarbonate and 0.10 wt. % to 4.00 wt. % of an acrylate-based scattering additive, 0.50 wt. %-5.00 wt. % of an aromatic polyester and 0.50 wt. % to 8.00 wt. % of a phosphorus-based flame retardant, based in each case on the weight of the overall composition, for extrusion applications.
Flameproofed plastics moulding compositions are used for a large number of applications. Typical areas of application for these plastics are electrical engineering and electronics, where they are used inter alia to produce supports for current-carrying parts or in the form of television and monitor housings. However, flameproofed plastics have also become firmly established in the sector of interior claddings in rail vehicles or aircraft. Here, in addition to good flame retardant properties, the plastics used must also display other positive properties to a high level. These include inter alia mechanical properties, such as e.g. high impact strength and adequate long-term stability towards thermal stress or towards possible damage by the action of light. This combination of properties is not always easy to achieve. It is true that the desired flame resistance can generally be established in plastics with the aid of flame retardants. Often, however, relatively large quantities are needed for this purpose, which rapidly leads to a drastic deterioration in other properties, such as e.g. mechanical properties.
Light-scattering properties of plastic can be adjusted by adding so-called scattering additives. However, the addition of organic scattering additives, particularly those based on acrylate, drastically impairs the fire properties of the composition, and large quantities of a flame retardant would have to be added to establish the required flame resistance.
It has now been found that the flame resistance of polycarbonate compositions containing scattering additives can surprisingly be increased significantly by a combined addition of small proportions of polyester and flame retardant additive.
WO 2002/059207 A describes flame retardant polycarbonate compositions containing cycloaliphatic polyesters. However, these cycloaliphatic polyesters have a high aliphatic proportion, which has an unfavourable effect on the fire properties of polycarbonate. Furthermore, they are more expensive compared with aromatic polyesters from the present invention. Mixtures with cycloaliphatic polyesters are not provided by the present invention.
In this connection, US-A 2003/0069338 discloses flame retardant moulding compositions that contain synergistic combinations of cyanoacrylates and flame retardants. The moulding compositions treated in this way are distinguished by improved flame resistance and improved weathering stability. Cyanoacrylates can, however, have an unfavourable effect on the processing behaviour of polycarbonate, e.g. at high temperatures. Mixtures with cyanoacrylates are not provided by the present application.
Mixtures that contain polyalkylene terephthalates and polycarbonates, and uses thereof, are known (cf. e.g. U.S. Pat. No. 3,218,372, DE-OS 1 694 124, U.S. Pat. No. 3,730,767, JP-A 7 401 639, U.S. Pat. No. 3,849,188, DE-OS 2 439 342 and DE-OS 2 708 381). The compositions according to the invention are not described therein, however.
Films and sheets based on polyester-polycarbonate mixtures which consist of no more than 50 wt. % polycarbonate and of at least 50 wt. % polyethylene terephthalate, and may optionally also contain other additives, are also known (cf. U.S. Pat. Nos. 3,956,229, 3,975,355 and DE-OS 26 47 565). The flame resistance of these mixtures is not discussed in these literature references.
Flameproof mixtures of polyalkylene terephthalates, organopolysiloxane-polycarbonate block copolymers and halogenated copolycarbonates, which are suitable for the production of films and sheets, are known (cf. U.S. Pat. No. 4,155,898). Mixtures of polyalkylene terephthalates, organopolysiloxane-polycarbonate block copolymers and CaCO3, which are likewise suitable for the production of films and sheets, are also known (cf. U.S. Pat. No. 4,157,997). Mixtures of specific halogen bisphenol polycarbonates and polyesters such as polybutylene terephthalates that have improved flame retardant properties are also known (cf. DE-OS 30 23 796).
EP-A 0 120 394 describes polycarbonate compositions with aromatic polyesters having improved flame resistance after outdoor weathering. This application does not, however, relate to compositions which contain scattering particles.
The sheets according to the invention are preferably of a multi-layer construction. Thus, they are preferably provided with a UV-protective layer, which is preferably applied in a coextrusion process. Extrusion materials of this type are described in the literature.
US-A 2006/0234061 describes multi-layer systems comprising a UV protective layer which contains polyalkylene (meth)acrylate and compounds of the type of the 2,4-bis(4-phenylphenyl)-6-(2-hydroxyphenyl)-1,3,5-triazines and a second, polycarbonate-containing layer. However, no improvement in the flame retardant properties can be achieved with these systems.
In U.S. Pat. No. 6,255,483 and in GB 2317174 A, biphenyl-substituted triazine compounds are described. Mixtures with other additives are mentioned in general terms. However, no specific teaching on the provision of compositions with improved flame retardant properties can be taken from the document.
It is an object of the present invention to provide compositions containing polycarbonate, which have improved flame retardant properties in combination with a high scattering effect. The compositions should be suitable for milky white coloured extruded products.